Germline multigene panel testing in colorectal cancer: Precision therapy and clinical management implications.

Abstract

3582 Background: Recent studies suggest that the prevalence of abnormalities in homologous recombination deficiency (HRD) genes and other cancer genes not traditionally associated with colorectal cancer (CRC) may be more common in patients with CRC than previously appreciated. Herein, we investigate the efficacy of comprehensive multigene panels in patients with CRC to identify candidates for precision therapies. Methods: DNA sequencing and exon-level copy number analysis were performed in over 9000 patients (pts) referred because of personal history of colon cancer between 2013 and 2018 at a commercial diagnostic laboratory. The genes requisitioned varied but consistently included 14 genes on a hereditary CRC panel; the patient data were de-identified and further analyzed for all 83 genes on a large hereditary cancer syndrome panel under an IRB-approved protocol. Results: Pathogenic/likely pathogenic (P/LP) findings were identified in 2101 of 9669 pts (21%), 1838 (19%) pts when MUTYH heterozygotes are excluded. When restricted to five Lynch syndrome (LS) genes, only 9% of patients had a P/LP finding, which increased to 15% of patients when 19 guidelines-based CRC genes were assessed. 137 pts (1.4%) had two or more P/LP variants. P/LP variants were in MLH1, MSH2, MSH6, PMS2, CHEK2, APC, MUTYH, BRCA2, ATM, BRCA1, PALB2, RAD50, BRIP1, TP53, EPCAM, among others, of which 1.4% were BRCA1/2. When a comprehensive multigene panel was utilized P/LP variants in genes with known therapeutic implications, such as in HRD and mismatch repair deficiency (MMRD), were detected in 1408 (14%) of patients, and 1670 (17%) had P/LP variants in genes with established clinical management guidelines. Conclusions: This study suggests that 1 in 5 patients with CRC harbor actionable germline variants, up to one-half of which remain undetected when only LS genes are tested. Comprehensive panel testing identified candidates for precision treatment and established management recommendations, and have clinical implications for both pts and their at risk family members.